Vehicle windows with electrical structures are known in the art. For example, vehicle windows such as backlites (i.e., rear windows) or windshields often have defoggers/defrosters, which include a conductive coating that is used to defog and/or defrost the window. The conductive coating for defogging/defrosting may take the form of a continuous substantially transparent coating having at least one conductive layer that is formed across a substantial portion of the window, or alternatively the conductive coating may take the form of a plurality of spaced apart parallel strips (heater bars), which extend across a significant portion of the window. In either case, there is a need to supply electrical current to the coating so that the coating is heated and defrosting and/or defogging can occur.
In order to provide electrical current to the coating, conductive bus bars are typically used. The conductive bas bars are typically made of silver (Ag) based frit and are thus electrically conductive. The silver frit bus bars are typically applied in their natural color, in rather wide bands used to convey sufficient current to/from the conductive coating.
Unfortunately, however, the silver frit of the bus bars tends to tarnish in an uneven manner over time to an undesirable brownish color. Wide bands of brownish colored material (tarnished silver frit bus bars) are unsightly, and aesthetically displeasing. Thus, those in the art have typically tried to hide such bus bars from view in the following manner.
Conventionally, a three pass process has been used to provide silver frit bus bars on a heatable window and then to hide the bus bars from view. First, in making a vehicle backlite for example, black enamel or paint is applied to the interior peripheral surface of the glazing (or window) in a strip proximate the periphery thereof. The purpose of this black enamel strip is to hide from view (from the vehicle exterior) the edge of the sheet metal window frame proximate the edge of the glazing, adhesive used to subsequently mount the glazing in the window frame, and/or the bus bars to be subsequently deposited. Second, after the enamel has been dried, the silver (Ag) based conductive frit is printed over the black enamel on the interior surface of the glazing, and is dried, so as to form bus bars located at least proximate the edge(s) of the glazing. The silver frit based bus bars are in electrical contact with the conductive coating, and are provided in order to supply current to the coating so that it can be heated. The conductive coating may have been formed prior to the formation of the bus bars, or alternatively at the same time the bus bars are formed using the same silver based frit to form a heat grid. Third, another black enamel strip is applied to the interior surface of the glazing (proximate only the periphery of the glazing) over the bus bars in order to hide the bus bars from view when looking from the interior of the vehicle.
While the process described above results in a vehicle window in which the silver frit bus bars are hidden from view, from both the inside and outside of the vehicle, the process is undesirable in that black layers are required to be applied on both the interior and exterior surfaces of the glazing/window adjacent the periphery thereof in separate steps.
Another prior art window is illustrated in FIGS. 1-2 (see also U.S. Pat. No. 6,625,875, the entire disclosure of which is hereby incorporated herein by reference). Referring to FIGS. 1-2, the windshield includes a conductive coating 3 having at least one conductive layer formed on glass substrate 2. In this example instances, the conductive heatable coating 3 includes a conductive layer 61 provided between at least first and second dielectric layers 63, 65. Edge deletion line 12 indicates the edge of the conductive heatable coating 3. Conductive silver frit bus bars 7, 9 are formed so as to be electrically connected to the transparent heatable coating 3. Electrical leads 8 are connected to the bus bars. Glass substrate 2 is laminated to glass substrate 4 via PVB interlayer 5 in a known manner. Black paint 51 is provided on the outer substrate 4 in order to hide the bus bars 7, 9 from view from the outside of the vehicle, whereas black paint 53 is provided on the interior substrate 2 in order to hide the bus bars 7, 9 from view from the interior of the vehicle. While silver frit bus bars 7 and 9 are hidden from view, from both the inside and outside of the vehicle, the process is undesirable in that black paint layers are required to be applied to both the interior and exterior substrates adjacent the periphery thereof in separate steps.
It will be appreciated from the above that there exists a need in the art for a vehicle window, and method of making the same, in which the conductive bus bars can more easily and/or efficiently be hidden from view.